The invention relates to an installation designed to determine the level and density of a liquid contained in a tank, using pressure measurements made by means of a bubble probe immersed in the liquid.
The invention also relates to a measuring method using said installation.
The installation and method of the invention find special application in the nuclear industry in order to conduct measurements in tanks containing radioactive solutions.
In the nuclear industry, when it is required to know the level and density of a radioactive solution contained in a tank, a static installation is frequently used such as the one shown in the diagram in FIG. 1 of the appended drawings.
Said installation customarily comprises two immersed bubble probes 1 and 2, dipping vertically into the liquid 3 contained in tank 4, so that their lower ends are positioned at different levels, separated by a distance of height Hd. The installation also comprises a reference probe 5, which leads into tank 4 above the free level of liquid 3. The three probes 1, 2 and 5 are the sole components of the installation located inside the contaminated zone.
Outside this zone, the installation comprises three flowmeters 6, 7 and 10, of variable section, through which each of bubble probes 1, 2 and 5 is supplied with compressed air at a slow flow rate and at a pressure of approximately 1.4 bars.
Finally, outside the contaminated zone, the installation comprises two pressure transmitters 8 and 9 and a calculator (not shown). Pressure transmitter 8 measures the pressure difference Pd between the immersed bubble probes 1 and 2, while pressure transmitter 9 measures the pressure difference Pn between immersed bubble probe 2 and reference probe 5. The calculator receives the pressure signals emitted by pressure transmitters 8 and 9 and calculates the density D of liquid 3, and the level N of this liquid, that is to say the distance of the latter above the bottom of tank 4, using the following equations: ##EQU1## in which Ho represents the height of the lower end of immersed bubble probe 2 above the bottom of tank 4.
Such measuring installations are frequently used and operate in satisfactory manner. However, their extended use has brought to light a certain number of disadvantages.
Firstly, having two bubble probes immersed into the liquid contained in the tank raises a problem of congestion as the inner space of liquid storage tanks is often already well taken up. This is particularly frequent in the nuclear industry.
Also, the complete installation is relatively costly since it comprises two immersed bubble probes and two pressure transmitters. Moreover, multiplying the number of components increases maintenance costs and the risks of contamination in the nuclear industry.